1. Field of the Invention
This invention is directed to a fluid sample distribution system for a test device. More specifically, this invention relates to a system and device for concurrent performance of multiple discrete analysis on a common test fluid by the passive and balanced distribution of the test fluid to the discrete test strips within the device.
2. Description of the Prior Art
The increasing popularity of simple and rapid diagnostic test kits for self-testing, and for use in professional environments devoid of elaborate instrumentation for sample preparation and analysis, has become increasingly prevalent because of the accuracy and relatively modest costs involved in the use of such products. Generally all of these products share the following common components, test format and performance criteria:
(a) a porous or bibulous medium for receipt of the sample, (which may also provide a source of test kit reagent for analysis of the sample), PA1 (b) a test strip specific for detection of an analyte of interest, PA1 (c) one or more test kit reagent(s) within the test strip that is (are) immobilized at a test site, PA1 (d) interaction of the sample with a test kit reagent in the test strip so as to produce a discernible physical change (e.g. color) at the test site of the test strip, PA1 (e) the ability to accommodate a relative substantial volume of sample (in comparison to automated/instrument based test systems), PA1 (f) manipulation of the sample to effect separation of endogenous sample constituents and unreacted test kit reagents at the test site, so as to produce a clean reaction product in the test site.
In a number of instances the methodology for performance of the such user oriented self-testing contemplates the application of a minimum volume (generally a substantial excess) of sample to the test device, so as to reconstitute the pre-disposed test kit reagents and thereby effect their interaction with the constituents of the sample. In order to effectively isolate the reaction products of such interaction within the test strip, either the analyte from the sample, or the reaction product of an analyte and a test kit reagent, become immobilized at a test site within the test strip, so as to cause a discernible physical change. For example, in the performance of a simple test for the detection of a drug of abuse, a test strip is provided with an immobilized binding substance that is specific for interaction with an epitope of the analyte of interest or a metabolite of the analyte of interest. Upon application of the sample to the sample collection web, the sample suspected of containing the analyte of interest, (e.g. cannabinoid compounds, where the test is specific for Marijuana), reconstitutes the test kit reagents in the sample collection web, (e.g. colloidal sold conjugated to an antibody specific for the analyze), and thereupon interacts with such test kit reagents to form an immunocomplex between the conjugate and analyte. This immunocomplex further reacts with the immobilized binding substance which migrates along the fluid pathway of the test strip to the test site within the test strip. As the immunocomplex becomes increasingly concentrated by the immobilized binding substance at the test site, a visible color, characteristic of the gold labeled immunocomplex appears. The appearance of this visible color is both time dependant and dependant upon the concentration of the analyte in the sample. More specifically, color development at the test site requires the concentration of the immunocomplex at the test site until the optical density thereof is sufficient to become visible to the naked eye--the so-called "direct indicator" of the presence of the analyte of interest.
In this type of assay, the volume of sample must be sufficient to provide sufficient analyte to produce the requisite concentration of immunocomplex necessary for visible color formation. This visualization of the immunocomplex is also (indirectly) dependent upon the absence of endogenous sample components at the test site which can interfere in such color development. Accordingly, such tests generally specify an amount of sample that can both satisfy the kinetics of the assay chemistry and, in addition, insure the requisite clean separation of the endogenous sample components from the immunocomplex at the test site. This clean separation can be more critical where, for example, the analyte is only present in very minute quantities, or where the test is biased to differentiate an elevated level of analyte from a basal level of analyte (e.g. analysis for HCG in pregnancy tests) within the fluid sample.
Historically, the performance of multiple analysis of a common test sample has generally required the use of automated instrumentation (Technicon SMAC Analyzer; Dupont ACA Analyzer; Baxter Healthcare PARAMAX Analyzer, and the like). This so-called "profile" analysis of a common test sample has also been postulated as capable for performance on a manual test device, however, it is believed that no such product has even been successfully produced, marketed and/or sold.
The ability to manipulate multiple samples, and/or perform multiple analysis within a common test device has, however, been described in the literature for use in conjunction with various assay formats, such as radioimmunoassay (RIA), fluorescence immunoassay (FIA) and enzyme immunoassay (EIA or ELIASA), U.S. Pat. No. 5,141,875 (to Kelton et at, issued Aug. 25, 1992). According to Kelton concurrent, multiple analysis of a common test fluid can be performed by "conjunctive centrifugation and wicking induced flow" of a sample by the dispensing individual aliquots of sample onto discrete areas of a sample receiving web within a rotary fluid manipulator of the type illustrated in his patent; and, thereafter applying an eluent to a common, centrally located reservoir, wherein such eluent flows from such common reservoir into each discrete fluid pathway and so as to cause the individual samples, in each discrete pathway, to migrate to a binding antigen specific for its detection and/or for further interaction with a companion reagent. As above noted, the label used in this analysis for the manifestation of the presence of the analyte of interest can be any of the common indicators, depending upon the assay protocol (FIA, RIA, ELISA).
Other patents and product literature showing manipulation of common test fluids within various test devices for performance of multiple analysis are well-known in the prior art, and typically include test formats analogous to chromatography, wherein a series of discrete and separate samples are spotted on a common the test medium, cross-migration therebetween inhibited by either physical isolation thereof or modification of the medium, or other common expedients, and a fluid carrier (generally containing a test kit reagent) applied to the medium to effect interaction of the sample and the test kit reagents.
As is evident from the foregoing discussion, there is and remains a continuing need for the development of an integral system for profile analysis of a common test sample to accommodate the needs of the self-testing environment of the individual, and of the professional testing environments lacking elaborate instrumentation. In order to be acceptable for use in either of these environments, the device and test protocol need be both compact and have the ability to distribute and contain a relative large volume of sample (which in a number of test situations) may include a highly infectious sample. In addition, the appropriate testing device need have the ability to conduct the prescribed panel of tests at essentially the same time, or concurrently, so as to afford availability of the test results for each of the assays within a precise time frame. Lastly, the successful test device design must be economic to produce so as to contain the cost of such test device to permit its availability to the broadest market for such kits. With respect to latter requirement, the achievement of this goal necessarily requires the ability to adapt existing test strips and test protocols to such a multiple assay delivery system. As is apparent from a review of the marketplace, the competitive product literature and the technical (patent) literature, no such device has as yet been suggested which can meet each of the above objectives. So long as this need continues, the consumer will be required to continue to purchase several different products to perform discrete assays to obtain comprehensive analysis of a single test sample for the information essential to monitor and/or diagnose body fluid constituents, which are essential to confirm a healthy condition and/or to diagnose a disease states.